Implantable leads represent the electrical link between an implantable medical device (often referred to simply as “IMD”) and a subject's cardiac or other tissue, which is to be excited or sensed. An implantable lead may include a single or multiple conductors that are connected to an electrode or an electrode assembly at a lead intermediate portion or a lead distal end portion. A connector is included at a lead proximal end portion to form an electrical connection between the electrode or electrode assembly and the IMD.
To implant a lead within the subject, the lead is often fed intravenously toward the subject's heart. On its way to the heart, the lead may be required to travel through vasculature having increasingly smaller diameters. Like any foreign body introduced into the vasculature system, the lead may present an obstruction to the normal flow of blood. The magnitude of blood flow area of a given vessel obstructed by the lead is, in part, a function of the diameter of the lead body. Once the lead is implanted within the subject and the electrode or electrode assembly is positioned at a desired location within, on, or about the subject's heart, it is often desirable to provide some active method and apparatus for securing the electrode or electrode assembly at such location.
After a lead has been implanted and secured as desired by an implanting physician, the lead may occasionally fail. Upon failure of an implantable lead, it may in some cases, as for example in pacemaker-dependent or defibrillator-dependent subjects, become necessary to implant a replacement lead. Replacement leads may also be required in situations where it is desired to stimulate or shock a different cardiac site than that stimulated or shocked with an existing lead. One potential issue of removing inoperative implanted leads relates to the application of a pulling force upon the lead proximal end. For example, the flexible sheath of leads that have been implanted within a subject for long periods of time may deteriorate over time as a result of exposure to the harsh in vivo environment.
Accordingly, there is a need for a lead having a lead body with a reduced size (i.e., outer diameter). In addition, there is a need for a lead having an intermediate portion or a lead distal end portion that may actively be secured at a desired location within, on, or about a subject's heart. Furthermore, there is a need for a method and apparatus for the extraction of inoperative leads.